1. Field of the Invention
The present invention relates to a branch connection structure for a flexible circuit belt, such as a flexible flat cable (FFC) or a flexible printed circuit.
2. Description of the Related Art
In general, a branch connector is used to branch off a flexible circuit belt, such as a flexible flat cable (FCC), and to electrically connect the flexible circuit belt to two or more circuits. Such a branch connector is generally attached to the end of the flat cable. A counterpart connector that is attached to another circuit to be connected receives this branch connector of the flexible circuit belt, thereby making electrical connection between two or more circuits.
FIGS. 1 and 2 illustrate a conventional branch connector for use with a flexible circuit belt. This type of branch connector is disclosed in, for example, Japanese Patent Application Laid-open No. 4-359875.
As shown in FIG. 1, the conventional branch connector consists of one ore more connection terminals 1. The connection terminal 1 has a male contact 2 at the leading end, which is to be received by a female contact of a counterpart connector. The connection terminal 1 also has a tall fork 3 with a height H1 and a shorter fork 4 with a height H2 (H2&lt;H1) near the trailing end.
FIGS. 1B and 1C show how a set of connection terminals 1 are attached to the end of a flexible circuit belt, which consists of two flexible flat cables 5 and 6. The connection terminals 1 are arranged in parallel to each other. A flexible flat cable 6 is superimposed on the FFC 5 so that the leading edge of the upper FFC 6 recedes from the leading edge of the FFC 6 by a prescribed distance. The forks 3 and 4 of each connection terminal 1 pierce through the superimposed flat cables 5 and 6, and the tips of the forks 3 and 4 are folded back in order to tightly hold the flat cables 5 and 6 together. In this manner, electrical connection between the flat cables and the connection terminals 1 are guaranteed.
To be more precise, the lower layer flexible flat cable 5 is held by the shorter fork 4, and the upper layer flexible flat cable 6 are held together with the FFC 5 by the taller fork 3.
The lower flexible flat cable 5 comprises a conductive layer 7 and a pair of insulating films 9 sandwiching the conductive layer 7, as shown in FIG. 1C. The upper flexible flat cable 6 comprises a conductive layer 8 and a pair of insulating films 10 sandwiching the conductive layer 8.
To complete a branch connection of the layered flat cables 5 and 6 (i.e., a flexible circuit belt) by the conventional connection terminals 1, the shorter fork 4 first pierces the lower flat cable 5. The tips of the fork 4 are bent using a piercing tool so that the tips stick into the conductive layer 7 of the lower flat cable 5. The flexible flat cable 6 is superimposed over the flexible flat cable 5 with its leading edge receding from the leading edge of the lower flat cable 5. At this time, the taller fork 3 pierces the upper flat cable 6, as shown in FIG. 2. The tips of the fork 3 are also bent using a piercing tool so that the tips stick into the conductive layer 8 of the upper flat cable 6.
With the conventional connection terminal 1, the piercing and bending steps have to be repeated twice. If three of more flat cables are piled, the same steps must be repeated as many times as the number of cable layers. The branch connection using the conventional connection terminals is time-consuming and requires much labor.
Another problem in the branch connection using the conventional connection terminal 1 is that the upper flexible flat cable 6 is stretched under a high tension when the branch connection assembly is applied to, for example, a wire harness device. A tensile stress is applied to the fork 3, which is pressing the upper flat cable 6 for electric connection, when the wire harness device is installed in an automobile door. As a result, the fork 3 deforms, which may cause the contact resistance to increase.